Figure 4.

Rpa1/Rpa2 photolabeling ratio during RDP growth at 0°C. Replicating SV40 chromosomes incubated at 0°C were pulse-labeled with BrdUTP and [α-³²P]dATP and chased with excess dTTP and non-labeled dATP. Aliquots withdrawn at the indicated time points were UV-irradiated and the photolabeled proteins digested with DNase I and further processed as in the Materials and Methods. (A and B) SDS–PAGE patterns of RPA subunits photolabeled during pulse-labeling or subsequent chase, respectively. The 5 min interval of UV-irradiation at 4°C is not included in the incubation times shown. (C) Rpa1/Rpa2 photolabeling ratios of (A and B). (D) Size distribution of nascent DNA chains of the indicated chase times.